Contact making device



Dec. 19, 1933. H. MARSHALL 1,940,176

CONTACT MAKNG DEVICE Filed July l5, 1955 E/ f 50 f z. f 34 12 20 7U [N VEN' TOR Patented Dec4.19, 1933 Y 'fcoNTAor MAKING DEVICE Hwardgm'arshall; Pittr Calif-j :iAppiicationiulyus, 1933. seriaiiNo. 680,621 A 4o1in'is.

This invention relates toA improvements in circuit controlling devices and aims to provide an inexpensive yet reliable device which will control a circuit in response to a predetermined rise of temperature.

A further aim of the invention is to provide a circuit control device in which contact elements are hermetically sealed in predetermined relationship by means of a meltable insulating subl0 stance, which substance also serves to prevent oxidation or corrosion of the contacts.

The invention will be fully apparent from the following detailed description when read in connection with the accompanying drawing and l will be defined with particularity in the appended claims.

In the drawing- Fig. 1 is an enlarged longitudinal section illustrating one embodiment of the invention in its normal position; Fig. 2 is a cross section on line 2-2 of Fig. 1; Fig. 3 is a view similar to Fig.

1, showing the relative position of contacts after a predetermined temperature has been reached.

In .the embodiment of the invention illusl trated, I have provided a shell-like casing within which is supported a block of rigid insulating material 12 slotted longitudinallyl as indicated at 14 and 16, to receive spring contact members 18 and 20, the contact points 22 and I 24 of which are normally held apart or in spaced relationship by a body of meltable insulating material 26. Circuit wires 28 and 30 are connected by terminal screws 32 and 34 to contacts 18 and 20. They may be connected in circuit with any suitable source of power, for example as indicated, by a battery 36 and an electrically operated element such as a signal bell or other device 38. The contacts 18 and 20 are preferably made of spring metal and are so constructed that they normally tend to move to the closed circuit position shown in Fig. 3. In assembling the device, the contacts are sprung apart and the melted insulating substance 26 is poured between them to hold them separated. 4| This operation may be carried on before the contacts and the supporting block 12 is nested in the casing 10. Then, after the body of said substance has solidied, the sub-assembly, consisting of the supporting block and the separated contacts is placed inside of the casing and the latter is lled with the same kind of molten insulating substance above mentioned, which upon cooling solidies and embeds the contacts in the position shown in Fig. l. Thus it is apparent that the separated contacts are hermetically sealed and are protected against the oxidizing iniiuence of the atmosphere or the corrosive action of gases which might tend to interfere with the proper closing of the circuit.

The device is not intended to operate repeatedly as a make and break device, but is intended to operate at once in a positive and unfailing manner. Devices heretofore in use frequently employed mechanical movements and the contact points over long periods of time are very likely to be inoperative when needed. This is particularly true when the circuit control device is used in circuits employing relatively small currents at low voltage. My improved circuit control device is particularly well suited for such low current and low voltage use. For example, it will work eiectively on currents as low as approximately 116 of an ampere with an electromotive force of one or two volts. With such low electrical characteristics, it is important that the contacts 22 and 24 be protected against corrosion and my improved device effectively meets this requirement. The device as used in practice is quite small and the inside diameter of the tubular casing (which may be either a circular or rectangular tube) is approximately 1A of an inch and has a length of approximately one inch.

The device being of such a compact nature can be readily placed in the Ventilating duct of a motor or cemented to a eld pole of a generator, or it can be placed inside of a bearing and will always be in condition to operate positively when a predetermined temperature is reached. It can be placed in warehouses in piles of material such as sugar, pulp, cotton, or other merchandise, or products which are liable to heat due to natural decay. It is also` adapted for closing a circuit to give a signal or an alarm in case the electrical wiring becomes overheated due to short circuit conditions.

While I have illustrated the device as normally intended to be held in open circuit condition by the meltable substance positioned between the contacts, it will be understood that similar spring contacts normally tending to separatecan be held in engagement with one another by a meltable substance, so that upon melting of the substance the circuit will be broken across the contacts. While not wishing to be limited to the use of any particular meltable insulating substance for holding the contacts in a predetermined relative position, in practice I nd that the `following substance may be relied upon to operate satisfactorily:

paran, bees-wax, sealing wax, resin, as well as other insulating compounds procurable on the market which melt over wide ranges of temperature,

Various modifications may be made by those skilled in the art Without departing from the invention as dened in the appended claims.

What I claim is:-

1. A circuit cl'osing device comprising a shelllike casing having therein a supporting block `of insulating material carrying spaced contacts at least one of which normally tends to approach the other and a body of meltable insulation retained by the casing and holding said contacts apart only so long as it remains unmelted.

2. A circuit closing device comprising a shell having therein a rigid insulating support carrying contacts, at least one of which normally tends to approach and close circuit with the other, and a meltable substance between said contacts designedly intended to hold them apart only until the melting temperature of said substance is reached.

3. A circuit closing device comprising a tubular casing, a rigid block of insulation secured therein, a pair of spring contacts normally tending to move to a point of engagement with one another. a meltable substance interposed between the spring contacts and substantially filling said casing, said substance designedly intended to hold the contacts in open circuit position only until the melting temperature of the substance is reached.

4. A circuit control device comprising a supporting block of insulating material with a shelllike casing, a pair of contacts carried thereby, and a meltable substance within 'the casing normally holding said contacts in a predetermined position relatively to one another and adapted when melted to alter said relative position of the contacts.

HOWARD MARSHALL.

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